The present disclosure is directed to a molten metal impeller having improved metal flow properties. According to one embodiment, a protective flow inducing cap member for a molten metal pump impeller is provided.
This disclosure generally relates to molten metal pumps. More particularly, this disclosure relates to an impeller suited for use in a molten metal pump. The impeller is particularly well suited to be used in molten aluminum pumps. However, it should be realized that the impeller can be used in any pump employed in refining or casting molten metals.
In the processing of molten metals, it is often necessary to move molten metal from one place to another. When it is desired to remove molten metal from a vessel, a so called transfer pump is used. When it is desired to circulate molten metal within a vessel, a so called circulation pump is used. When it is desired to purify molten metal disposed within a vessel, a so called gas injection pump is used. In each of these types of pumps, a rotatable impeller is disposed within a pumping chamber in a vessel containing the molten metal. Rotation of the impeller within the pumping chamber draws in molten metal and expels it in a direction governed by the design of the pumping chamber.
In each of the above referenced pumps, the pumping chamber is formed in a base member which is suspended within the molten metal by support posts or other means. The impeller is supported for rotation in the base member by means of a rotatable shaft connected to a drive motor located atop a platform which is also supported by the posts.
An exemplary pump in which the impeller of this disclosure can operate is depicted in FIG. 1. FIG. 1 depicts the arrangement of the impeller 14 in a molten metal pump 32. Particularly, a motor 34, is secured to a motor mount 36. A riser 38 (indicating this pump to be a transfer-style) through which molten metal is pumped is provided. The riser 38 is attached to the motor mount 36 via a riser socket 40. A pair of refractory posts 42 are secured by a corresponding pair of post sockets 44, a rear support plate 46 and bolts 48 to the motor mount 36. At a second end, each of the posts 42, and the riser 38, are cemented into a base 50. The base 50 includes a pumping chamber 52, in which the impeller 14 is disposed. The pumping chamber is constructed such that the impeller bearing ring 10 is adjacent the base bearing ring 54. The impeller is rotated within the pumping chamber via a shaft 59 secured to the motor by a threaded connection 60 pinned to a universal joint 62.
Obviously, there is a desire to increase the efficiency of a molten metal impeller. Improving the flow of metal into the impeller is one mechanism by which this is achieved. It is a further desire to limit the degradation of the impeller. Moreover, to operate in a high temperature, reactive molten metal environment, a graphite material is typically used to construct the impeller. Graphite is prone to degradation when exposed to particles entrained in the molten metal. More specifically, the molten metal may include pieces of the refractory lining of the molten metal furnace, undesirables from the metal feed stock and occlusions which develop via chemical reaction, all of which can cause damage to an impeller.